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Use cases also have the roles of functional requirements. How does this harmonize
with the requirements we determined in Section 2.2? A use case is a
FIGURE 2-37
Model showing the results of the use case workshop.
pkg Use case packages
Service
Navigation system
Radio
Phone
Poll system
status
Do
system test
Configure
on-board
computer
Start on-board
computer
Car usage
Start
car usage
Show
car usage data
End
car usage
73
refi nement of a functional requirement. It fulfi lls further criteria, such as domain
trigger, result, and time coherence. It has actors associated with it, and an activity
describes the fl ow in detail (Section 2.4.5).
Functional requirements are more general in nature and are not subject to
side conditions. The refi ne relationship ( Figure 2.38 ) describes how a functional
requirement and a use case relate. It could easily be that several use cases refi ne
one single requirement, just as well as one single use case can have refi ne relationships
with several requirements. A use case is an element of the analysis, but not a
requirement.


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